Exercise Info, Not Calorie Counts, Helps Teens Drop Sodas

Sugary drinks like soda are a big cause of obesity, but public health types haven't had much luck convincing the public of that.

But what if you knew that it would take 50 minutes of jogging to burn off one soda?

When researchers taped signs saying just that on the drink coolers in four inner-city neighborhood stores, sales of sugary beverages to teenagers dropped by 50 percent. That tactic was more effective than a sign saying that the drinks had 250 calories each, or a sign saying that a soft drink accounts for 11 percent of recommended daily calories.

"I was skeptical," says Sara Bleich, an assistant professor of health policy at the Johns Hopkins Bloomberg School of Public Health, who led the study. She wasn't sure if the low-cost intervention would work, or if it would work with the low-income African-American teenagers that was the target audience. But it did.

To test the idea, Bleich and her colleagues picked four corner stores near middle and high schools in low-income neighborhoods in Baltimore. Each sign, which was a simple piece of paper, was tested separately, with a grad student in the corner quietly writing down teenagers' purchases as they hit the counter.

The signs stating the percentage of daily caloric intake in a soda reduced sugary purchases by about 40 percent, while merely listing the calories in a drink (which is already listed on the bottle) seemed to have no effect. Instead of buying soda or fruit juice, many kids who read the sign picked water instead. The work was published today in the American Journal of Public Health.

The new federal health care law requires restaurants and vending machines to start labeling the calorie content of food and drink, in an effort to encourage healthy choices. That's expected to kick into gear next year.

Health experts are worried in part because beverage companies increasingly target black and Hispanic kids more than others in their ads. From 2008 to 2010, children's and teens' exposure to television ads for soda doubled, according to a recent report from the Rudd Center for Food Policy & Obesity at Yale University.

But Bleich say her study suggests that it might be better to think about other ways to give people a sense of the caloric load in a soft drink. "Why is it that the minutes of jogging was most effective?" she asks. "My personal feeling is that jogging works because it's a negative thing."

She's going to test that idea by continuing the experiment with signs listing minutes of basketball or minutes of dancing.

Copyright 2011 National Public Radio. To see more, visit http://www.npr.org/.

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